Photographic means for recording sound



June 15 1926. 1,588,884

R. HART PHOTOGRAPHIC MEANS FOR RECORDING SOUND Filed Dec. 22, 1922 UUUOUUUUEIDUUUUUUUU as as E I 0 32 7 a r E 5 J2 J3 5 J6 Inventor; jiusSeZZ Hart,

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Patented 19 26.

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l PEOTOGBAP HIC MEAN S FOB RECORDING SOUND.

Application filed December 22, 1922.- Serial No. 608,499.

( My invention relates to means for photographically recording sound modulated light variations upon a moving sensitized film; and the salient objects are, first, to pro- ,vide a source of light that is highly sensitive to sound waves, including the overtones,

, and capable of respondingto qual ty vibrations'as well as to intensity and pitch; second, to secure very high responsive s ced of the light to sound variations; and, t 1rd, to afford facilities for photographically recording the responsive action of the light in such a manner-as to constitute a complete and undistorted sound record.

Other highly important objects are to supply means for producing a sound record of great sharpness so as to permit, for example, of practically perfect reproduction of articulated voice; and to accomplish the recording at a film speed far below that hitherto possible, and corresponding to the speed commonly employed in the taking of motion pictures.

Additional objects and advantages of my invention will appear'hereinafter, and while I show herewith and will describe a preferred form of construction to accomplish must include; a source .of light of high actinic value; the elimination of diffraction; very accurate focusing; and the prevention of all forms of distortion of the record so faras this can be done.

Hitherto a narrow slit in close proximity to the film has been used, and the modu lated light has been focused thereon by various means. It is well known that light in passin greater will be the diffraction. It is impracticable .to run a film directly against any known form of slit, and runners that space the film at least of an inch from the slit have therefore been employed. Both of these facts militate against sharpness of the record, and cause blurring in the reproduced sound. r l.

I The filmspeed that is normally employed inthe taking of motion pictures is one foot such a slit is diffracted at each side 7 thereo and that the narrower the slit the per second. To record articulated voice at this speed I have found that the slit must not exceed of an inch in width to get fair results. If such a slit is used in the hitherto known way, the image, with the relativity great diffraction that is present, 'when cast upon a film T701 of an inch distant, will necessarily be blurred and thus make it impossible to secure good articulation in the reproduction.

In the present invention an image of the slit is thrown upon the film by means of a suitable achromatic lens combination, thus entirelyobviating the effect of slit diffraction, and making it possible to reduce the image to any desired degree of fineness and sharpness. The finer and sharper the image of the slit can be made to appear, the slower the film can be run, and I have found it possible withmy improvedmeans to satisfactorily record music and articulated voice at film speeds of one foot per second or even ess.

In the accompanying drawing Figure l is a side elevational view of a typical arrangement of my invention, with certain parts broken away and in section;

Figure 2 is a sectional plan view taken on the line 2-2 of Fig. 1

Figure 3 is a cross sectional elevation taken on the line 33 of Fig. 1;

Figure 4 is a sectional plan view of a portion of the manometric flame apparatus employed as. a source of light in the illustrated apparatus. This View is drawn to a larger scale than those previously mentioned;

Figure 5 is an enlarged elcvational detail of a portion of the means employed for ad-,

justing the position of the manometric flame;

Figure 6 is a fragmentary sectional elevation taken on the line (r-6 of Fig. 2;

Figure 7 is an enlarged en'd elevation of a preferred form of optical slit, and the means employed for adjusting its position angularly and transversely, and

Figure 8 is a fragmentary elevation of a film with a photographic sound record thereon, as produced by my improved means.

Similar numeralsrefer to similar parts throughout the several views.

Before passing to the detailed description of my apparatus it should be understoodv that the present invention involves only the means for photographically recording sound. It does not concern itself with the reproduction per se, for which practical methods have been devised.

In the embodiment of the invention selected for illustrative purposes the apparatus is mostly contained within an elongated light-proof box-like structure, or camera, 8, preferably supported by table legs of which one is shown at 9. The camera 1s interiorly divided by a transverse partition 10, forming two main-chambers to which access is had through the hinged trap doors 11 and 12. Above and below the right hand chamber of the camera are reel boxes 13, having side opening doors 14, and communicating with tne camera only by means of small narrow slits 15 for the passage of the photographic film strip 16.

, In the present instance I have selected a manometric flame 17 as the source of light. This may be an oxy-acetylene, or any other suitable flame of high actinic value, properly arranged for sound modulation. As illustrated the modulating apparatus comprises the horn 18, diaphragm box 19, diaphragm 20, and gas burner 21.

The combustible gas, as acetylene, is stored in tank 22 and passes to the burner through a regulating valve 23, hose 24, and nipple 25. Similarly oxygen is supplied from tank 26 through regulating valve 27, hose 28, and nipple .29.

The combustible gas in the burner is in free communication with one side of diaphragmv 20 through tube 30. The sound receiving horn is in free communication with the otherside of this diaphragm through tube 31. Sound waves entering the horn impinge on the diaphragm and cause it to vibrate responsively. This modulates the gas pressure in the burner and produces a manometric effect upon the flame. The respective static gas pressures in the burner are preferably so adjusted as to produce a thin, elongated, needle-pointedflame of great actinic value. In this way the modulating effect of the diaphragm may be made to vary the length of the flame in accordance with the character of the sound waves received in the horn. a

At the point 32 an extremely tenuousoptical slit is adjustably mounted. This may be made by depositing platinum or other suitable opaque substance upon a piece of glass 33, as shown at 34, and then making a very fine line scratch 35 through this opaque deposit.

In my improved arrangement light from the flame passes through a suitable condensing lens combination at 36 and is focused upon slit 35. The image of the illaminated slit is then thrown upon film 16 by means of a suitable achromatic lens'combination 37. Since the film and its sensitized coating is sufficiently transparent, the focusesaesa ing at this point may be accomplished by means of a microscope 38, co-axial with the camera, and permanently mounted thereon. It is possible to secure an exceedingly sharp focus in this way.

Obviously various adjusting means are required to secure the desired results. These are roughly indicated in the drawing but the co-operating parts should be accurately made in a manner permitting of exact manipulation.

The flame preferably should intersect the axis of the camera. The illustrated means of accomplishing thisis by mounting the burner on the bent arm 39 pivoted in the camera axis. This arm is engaged by the channelled fitting 40 and may be given any desired angular position by means of the hand Wheel 41 which is in fixed co-operative relation therewith. Transverse adjustment of the arm is permitted by slotting it as at- 42 in Fig. 5. The through bolt 43, and wing nut of the burner.

As shown in the drawing the condenser is focused by means of hand wheel 49, pinions 50, and rack bars 51; the condenser being mounted on the frame 52 which is slidable on rails 53.

Opticalslit 35 is positioned vertically by means of the screw 54, and angularly by the gear 55 and worm 56, operated by hand wheel 57.

' Iiens combination 37 is mounted in the telescoping tube 58 and is focused by means of the rack 59, pinion 60, and hand wheel 61.

The form of microscope shown is focused by means of the barrel screw 62.

Other features of the camera box proper include the small hooded inlet. ventilators 63, below the flame, and the large hooded outlet ventilator 64 above it.

For photographically recording sound the film strip must be given a continuous uniform motion, and I prefer to usea synchronous electric motor for this purpose.

The driving means should be positive in character and the film mustbe constrained to lie perfectly fiat at the point where it is being exposed. It must also be prevented from chattering or vibrating as the result p ll iled to sprocket shaft 70, as by pulley 71. e other sprocket shaft 72 also carries a pulley 73, by means of which the take-up reel is yieldingly driven.

While being exposed, the film in the gate mechanism passes between two polished plates 74 and 75. These are pressed together by light spiral springs 76 surrounding the guide screw studs 77 in the manner common to the art. Flatness of field is positively secured in this way, the exposure being had through small apertures 1n the plates in front of the film, as indicated at 78.

In operation the slit must be maintained parallel relation to the flame at the focused image of the latter. The length ofthe camera should be kept as smallas possible to reduce the effect of vibration, and the apparatus should be rigidly supported in such a manner that delicate adjustments can be made and maintained. The manometric flame may be used either in a horizontal position as shown, or in vertical osition.

As described, and illustrated 111 Fig. 8, the sound record com rises an exposed area 79 bounded on one side by the base line 80, and on the other side by a very irregular curve 81 corresponding to the complex shape of the sound waves. There is com aratively little variation in density throng out area 79, and for reproduction of sound reliance is chiefly had upon the variation of the ordinates of the curve. The modulated manometric flame however does vary somewhat in intrinsic brillianc and this effect is recorded b corresponding changes in the density of the record which have their proportional effect upon the reproduced sound.

Instead. of employing a light source modulated as here illustrated, it is erfectly feasible with my apparatus to ma e use of any suitable light source, and any known means of modulating the same by sound. Thus it is possible to employ a light source of fixed dimensions, modulated wholl with respect to its intrinsic brillianc uch a source might comprise an incan escent filament operated at a very high temperature, and modulated electromagnetically. In such case the photographic sound record would consist of an exposed band of constant width, but varyin greatly in density. Such a record mightlw said to be in and out of the film as distinguished from the back and forth type herein shown.

Having thus fully described my invention in a manner that Wlll be readily understood,

I claim;

1. Sound recording apparatus com rising; means for producing an attenuate actinic flame; a photo-sensitized surface, means for moving saidsurface at a uniform velocity; an intermedite opaque screen having a tenuous optical slit parallel to the flame, whereby a thin beam of actinicrays from the flame may be thrown upon said surface transversely to its direction of motion; and means for modulatin the visible length of said flame by soung waves, to vary the width of said beam.

2. Sound recording apparatus comprising; means for producing an attenuated actinic gas frame; a photo-sensitized surface; means for moving said surface at a uniform velocity; an intermediate opaque screen having a tenuous optical slit parallel to the flame, whereby a thin beam of actinic rays from the flame may be thrown upon said surface transversely to its-direction of mo:-

tion; means for variably positioning the slit transversely and angularly in its own plane; and means for modulating the visible length of said flame by sound controlled variations. in thepressure of its combustible gas supply, to vary the width of said beam.

3. Sound recording apparatus com rising; means for producing an attenuated actinic gas flame; a photo-sensitized surface; means for moving said surface at a uniform velocity; an intermediate opaque screen having a tenuous optical slit parallel to the flame, whereby a thin beam of actinic rays from the flame may be thrown upon said surface transversely to its direction of motion; means for variably positioning the slit transversely and angularly in its own plane; and an acoustic diaphragm in contact with the combustible gas sup 1y of the flame. adjacent its burner, where y the visible length of the flame may be moduIatedJby sound waves, to var the width of said beam.

4.- In soun recording apparatus, a sound controlled actinic flame device comprising; a burner having inde endent supply connections for oxygen and combustible gas; and

an acoustic diaphragm in contact with the combustible gas sup ly adjacent the burner, whereby the visible length of the flame may be modulated by sound waves.

5. In sound recording apparatus, a sound controlled actinic flame device comprising;

a burner tip having a tubular outer shell adapted for connection to an oxygen'supply; a concentric inner tube terminating within said shell adjacent its outlet, and adapted for connection sup ly; and a chamber communicatin with sai inner tube adjacent the burner tlp and having an acoustic diaphragm therein whereby the pressureof the combustible gas may be modulated by sound waves, to vary the visible length of said flame.

' RUSSELL, HART.

to a combustible as 

